Method of and apparatus for making gears



March 4, 1.930. w. E. HOKE 1,749,670

METHOD OF AND APPARATUS FOR MAKING GEARS Filed March 15, 1928 2 Sheets-Sheet l March 4, 1. 930.

w. E. HOKE METHOD OF AND APPARATUS FOR MAKING GEARS Filed March 15, 1928 2 Sheets-Sheet 2 Patented Mar. 4, 1930 WILLIAM E. noxn,

OF BALTIMORE, MARYLAND METHOD OF AND APPARATUS FOR MAKING GEARS Application filed March 15, 1928. Serial No. 261,874..

This invention relates to a method of and apparatus for making gears, and more particularly to a method of and apparatus for making precision complementary gears.

The finishing of gears by lapping operations is well known, and in my prior Patents 1,486,338 and 1,486,339, I have described a method of lapping which results in the formation of a plurality of identical gears. By

lapping a plurality of gears with a precision rack, and periodically shifting the position 7 of some of the gears upon the rack, a symmetrical distribution of the errors in the aggregate surface being finished can be obtained and identical gears may be formed.

When two gears formed in this manner are meshe they will fit more accurately and will run with less noise than is possible with gears which are finished in other manners.

2 The two gears are identical but they nay not be exact complements of each other.

An object of the present invention is to provide a method of and apparatus for making identical sets of precision complemental gears. A further object is to provide a method of forming precision complemental gears by' first forming a pair of precision complemental laps, and then lapping one of the gears with one lap and lapping the second gear with the complemental lap. A further object of the invention is to provide a pair of complemental precision laps for use in the finishing of complemental precision gears.

These and other objects of the invention will be apparent from the following specification when taken with the drawings, in which-' .Fig. 1 is a fragmentary plan view, with parts shown in section, of apparatus for lap- 40 ping a plurality of identical gears,

Fig. 2 is an end elevation of a palr-of complemental gears, one gear being of the form shown in Fig. l,

Fi 3 is a fragmentary plan view illustrat- 'ingt e method of forming the complemental laps, and

Figs. 4 and 5 are diagrammatic views illustrating the finishing of the respective gears of-a complemental pair.

accompanying cured in ment being that at In Fig. 1, the numeral 1 indicates a'shaft which is mounted between dead centers 2 of a lathe and provided driven from the usual dead center whirl, not shown. A pair of like gear blanks A, A, whose errors are to be removed by lapping, are mounted on shaft 1, the gear A being seposition against a peripheral shoulder 4. on shaft 1 by a threaded collar 5, and the second gear A being adjustably clamped in place between the two threaded collars 6, The particular mechanism for mounting the gears is not important; the only requireleast one of the gears can be adjusted angularly 0r longitudinally of the shaft to eliminate back lash.

The gears A, A" both mesh with an elongated lapping gear a: which is mounted upon dead centers 8 with its axis parallel to the axis defined by the dead centers 2. When the lapping operation is carried out on the usual type of lathe, the dead centers 8 are preferably mounted upon the tool slide.

As shown in Fig. 2, the gear A (or A) is to mesh with a complemental gear B, and preferably gears A and B are of the hunting tooth type, that is, the number of teeth on gear A is not a multiple of the number of teeth on gear B. As illustrated, the gear B has 36 teeth, while gear A has one less than twice that number, or 71 teeth. Where otherwise practical, I prefer to employ the hunting tooth principle in the design of the gearing as it facilitates the lapping of th gears, but it is to be understood that the invention is not limited to the formation of such gearing as I can readily form precision complemental gearing having any desired ratio of teeth or the same number of teeth.

An important feature of my invention relates to the formation of the elongated helical lapping gear a which is employed in lapping the series of gears A for the complemental pairs of gears, A, B. As indicated in Fig. 3, the lapping gear a is worn in, or lapped by a complemental lapping gear I), and the two lapping gears a, 6 preferably have the same number of teeth as the gears B, A, respectively, of the pairs of gears which are to be formed.

The lapping gears a, b are formed of suitwith a dog 3 which is able metal in accordance with the composishown in Figs. 4. .plng gears are made narrower than normal place.

*ery, carborundum,

are worn in on each other in accordance with the principles set forth in my prior patents .to effect a symmetrical distribution of the errors, and to produce precision gears. en

the lapping gears are formed of cast iron,

suitable abrasives for lapping the gears upon each-other are of the non-charging type, such askDiamondtine,.Vienna lime, rouge or t e By employing lapping gears a, b of the same diameters as the respective gears B; A, the lapping gears may be worn in upon the same lathe or machine which is to be used for the formation of the finished gears. This feature is desirable, and may become'quite important if the cross-feed of the lathe does not travel forward in a straight line, or should tip slightly in its forward movement.

The lapping gears are worn in by running them in mesh with each other, the gears beingv given a relative longitudinal movement by suitable means, for example, the usual feed screw is employed to move one gear when the work is carried out on a lathe. At intervals one of the gears is reversed end for end to bring different portions of the gears into engagement during the lapping process.- When the lapping gears are of the hunting tooth type it will not be necessary to shift the gears angularly during the lapping process as the gears will, of themselves, bring each tooth of one gear periodically in mesh withlapping gears and precision complemental every tooth of theother gear.

When the lapping is completed, the gears a, b will be precision complemental gears with an accurate helix'angle, and both sides of each tooth of each gear will be accurate as to spacing, profile and concentricity.

Having formed the complemental lapping gears a and b,.these gearsare then employed to finish the gears A and B, respectively. As

and 5, the teeth of the lapteeth, and are given an excess addendum.

Reverting to Fig.1, the method of lapping gears A, A is carried out in the following manner: The gear A is secured in place by the collar 5, and the gear A'- is loosely held in The tool slide carrying dead centers 8 is then moved forward to carry'lapping gear a into mesh with both A and A. -As the gear A is loose upon shaft 1, and the teeth of gear a are relatively narrow, the slide may be moved forward until the addendum ofthe lapping gear teeth projects into the clearance or non-active space at-the base of the teeth of gears A, A. The gear A' is then moved longitudinally of the shaft 1 to eliminate back lash in one direction and is clamped in place by collars 6, 7. Lapping gear a is charged with a suitable abrasive such as emaloxite or the like and the gears are rotated by the dead center whirl and dog 3. The lapping gear a is moved longitudinally by means of the feed screw, and, from time to'time, the direction of rotation of the gears is changed, and gear A is shifted to the other limit of its range of movement to take up back lash in the opposite direction. After a period, the lapping gear is moved out of mesh with gears A, A, A is loosened and moved angularly, with reference to gear A, by 180 or more. The lapping gear is then returned and gear A is again adjusted to eliminate back lash and the operations are repeated.

When gears A, A are finished, a pair of gears B are placed on shaft 1, lapping gear I) is substituted for gear a,'and the lapping operations are continued until both gears are worked into identical form.

\Vhen sets of gears A and gears B are completed, all gears of each set are identical and any gear of oneset is an accurate complement for any gear of the other set. Due to the excess addendum of the lapping gear teeth the entire active surfaces'of the teeth of the complemental gears are accurately finished, and any shoulders which may be formed by the lapping are located in the clearance space at the roots of the teeth. Theuse of, the hunting tooth principle is decidedly advantageous and preferably the lapping gears should e111- body that principle not only as regards each other but also as regards the gears which they are to finish, but while desirable this is not essential, as precision complemental and the gear support may be employed for carrying out the work. Iclaimr I 1. The method of forming a pair of precision complemental gears which comprises forming a pair of complemental precision laps by lapping the same" upon each other, and forming the gears of said pairby lapping the same with't-he respective laps of the complemental precision laps.

2. The method of forming pairs of complemental gears which comprises lapping .upon each other a pa1r of complemental lapping gears, shifting the angular and longitudinal relationship of the said lapping gears during the lapping operation to effect a symmetrical distribution of the errors,

a plurality of like gears with one of said lapping gears to produce a set of identical app e meaeao gears, and lapping a plurality of complemental gears with the other lapping gear to produce a second set of identical gears, whereby any pair of gears selected one from each of said sets of identical gears will be complements.

3. The method of forming pairs of complemental helical gears, which comprises lapping upon each other a pair of elongated helical gears to formcomplemental lapping members having teeth which are precise as to profile, spacing and concentricity, and employing one of the lapping members to lap a plurality of like gears, and employing the other lapping member to lap a plurality of like gears.

4:. The method of forming complemental helical gears which comprises running a pair of helical lapping gears in mesh with a noncharging abrasive, producing relative angular and axial displacement of said lapping gears and reversing their directions of rotation while running them in mesh, whereby precision complemental lapping gears are formed, lapping a plurality of gears with one of said complemental lapping gears and lapping a plurality of gears which are to be made complemental to the-said plurality of lapped gears with the other lapplng gear,

5. Apparatus for lapping sets of complemental helical gears comprising a pair of helical lapping gears having an axial length materially in excess of the axial length. of the complemental gears to be formed, said lapping gears having teeth with excess addendum, the tooth spacing of the said lapping gears being accuratebut the tooth width being narrower than the spacing of the teeth on the gears to be formed, and both faces of all teeth of both complemental lapping gears being accurate as to profile, spacing and concentricity.

In testimony whereof, I aflix my signature. WILLIAM E. HOKE. 

